More tips to keep your diet on track

Rightly or wrongly, I have always found carbs to be my friends. I frequently consume my own body weight in pasta at about 9pm after work, and when making sandwiches, no fewer than four slices will do. So when I took a DNA test to learn what kind of diet best suited my genetic make-up, the results came as a blow. I'd expected to be told I should follow a Mediterranean regime because, well, shouldn't everyone? Instead, I was advised to switch to a low-carb plan. It was sufficiently sobering to make me pause, my sandwich halfway to my lips.

This revelation about where I was erring gastronomically came courtesy of DNAfit, a genetic testing company with the catchline: ‘One test. A lifetime of change.’ The firm recently teamed up with restaurant chain Yo! Sushi to offer a personalised eating plan tailored to one's DNA – calculated via a test tube of saliva, from which a large amount of data can be extracted.

For instance, my results told me I am not lactose intolerant (which I already knew); that I have a normal sensitivity to alcohol (debatable, and probably depends who you ask); that I have a raised sensitivity to salt (might this explain my crisps addiction?) and a slow sensitivity to caffeine (surprising, given the speed with which I come up on coffee). A low-carb diet plan was recommended because, apparently, I have a high sensitivity to carbohydrates.

‘But I'm not obese,’ I protest to Amy Wells, lead dietitian at DNAfit. ‘And neither is anyone in my family. So what does this actually mean?’

‘It relates to your insulin response,’ she explains. ‘So with your high carb sensitivity, you will see a higher insulin response to a high carb intake. In the long run, it increases your risk of type 2 diabetes.’

This is not the news I've been hoping for, but since no one in my family has ever been known to ration carbs, nor battle this illness, I remain sceptical about just how concerned I should be.

‘We're looking at environment in conjunction with genetics, so it's about the way your genes interact with the environment,’ says Wells. ‘If you're eating a high-carb plan but the bulk is sugar or refined carbs, your risk would be higher than if you're eating a lot of starch. How physically active you are will also play a part.’ And the test is non-diagnostic, she stresses. ‘It's guiding you on what lifestyle adjustments to make.’

The idea that genes play a role in our propensity to gain or shed the pounds is certainly appealing, and with new advances in genetic testing, growing numbers of companies are selling the dream of ‘nutrigenomics’ – personalised nutrition plans that offer advice on foods to eat and avoid according to your DNA profile. Home testing kits can retail for as little as £59 (Dh270). All the user has to do is take a swab from inside their cheek and send it to a lab to be analysed, completing a basic questionnaire. But can such tests really deliver that holy grail – a diet that works?

Another analysis, MyDNA at Lifelab Testing, tells me I have a gene that helps me store fats for future energy needs, which is ‘great in times of famine’ but ‘not ideal for your beach bod goals’. According to my report, people with my result have noticed they have a higher body mass index. Mine has always been low. The report does add that ‘if you're trim... your lifestyle is counteracting your genetics’. As a sedentary worker with a serious pasta habit, I'm really not sure that it is.

Further down the report, I learn I have another genetic variation that has no association with a higher BMI. Do the two, therefore, cancel each other out?

This month, a major study raised questions over the value of DNA diet plans. Research on 1,100 people by King's College London, and Massachusetts General Hospital and Stanford University in the US, found that genes only partly explain the fact that different people have different responses to the same foods.

By looking at identical twins, who share the same genetic make-up, the researchers were able to see the limitations of the influence of genes in how we metabolise what we eat. It turns out that environmental factors such as sleep, stress, exercise, the times at which we eat and the state of our gut microbiome, may all be just as important in determining how the body responds to food.

The findings came as a surprise, even to the researchers.

‘What we found by capitalising on the data from twins is that less than 50 per cent of our glucose response is due to genetic factors, less than 30 per cent for insulin and less than 20 per cent for our triglyceride, or fat responses. So the large variation [in how people respond to food] is only partly explained by genetics,’ says Dr Sarah Berry, a senior lecturer in nutritional sciences at King's, who worked on the study.

‘This is exciting because it shows it's not all in our genes. In fact, only a tiny bit is, so it's mostly modifiable. It's empowering, because how you're going to respond is not predefined.’

In other words, the first generation of DNA diet plans, like the ones I road tested, probably don't hold the secret of easy weight loss.

‘Given that genetic factors play a relatively minor role in determining our responses to food, we need to be very cautious on putting too much weight on it,’ says Dr Berry.

Dr Frances Elmslie, a consultant clinical geneticist at St George's University Hospitals NHS Foundation Trust, also sounds a note of caution. ‘The science... is not powerful enough to predict independently of all the other risk factors [something like obesity or diabetes].’

‘I see it as this whole commodification of what's so essential about being human,’ adds Dr Luke Kane, a London GP. ‘All you need to do to live a happy, healthy life is eat normal food that's not too processed, and lots of vegetables. There's no quick fix or magic bullet.’

That's not to say that personalised nutrition has no future. This research supports the idea that a one-size-fits-all approach to diet doesn't work – it's just that a DNA test may only provide part of the answer.

‘One of the key findings was that genetics accounted for roughly 20-50 per cent in the variance… the more pieces of the overall dietary puzzle we have, the better we can guide our customers to personalised actions,’ says Dr Keith Grimaldi, at DNAfit.

Dr Berry and her colleagues' ultimate goal is to create a more comprehensive home-based test to enable everyone to understand their own nutritional responses, integrating lifestyle, microbiome and other data. It is hoped this will become universally available as an app from next year.

Dr Berry, though, is generally wary of fuelling an obsession with what we put in our mouths, and says ‘the whole denial thing’ can be a problem.

‘Food is there to be enjoyed,’ she says. ‘It's a pleasure, a social event. I don't think you should deny yourself anything.’

The Daily Telegraph